May 2008
Volume 49, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2008
Posterior Corneal Shape Changes With Overnight Corneal Edema in Rigid Conventional and Orthokeratology Lens Wear
Author Affiliations & Notes
  • J. H. Yoon
    School of Optometry and Vision Science, The University of New South Wales, Sydney, Australia
  • H. A. Swarbrick
    School of Optometry and Vision Science, The University of New South Wales, Sydney, Australia
  • Footnotes
    Commercial Relationships  J.H. Yoon, None; H.A. Swarbrick, Bausch & Lomb, BE Enterprises, Capricornia Contact Lenses, F.
  • Footnotes
    Support  Funded under Australian Government's ARC Linkage Scheme
Investigative Ophthalmology & Visual Science May 2008, Vol.49, 4848. doi:
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    • Get Citation

      J. H. Yoon, H. A. Swarbrick; Posterior Corneal Shape Changes With Overnight Corneal Edema in Rigid Conventional and Orthokeratology Lens Wear. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4848.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : To evaluate the influence of overnight corneal edema on posterior corneal shape during sleep, and conventional and orthokeratology (OK) rigid gas-permeable (RGP) lens wear.

Methods: : Eighteen young adult subjects (19-32 yrs) with low myopia (<-4.00D) and astigmatism (<1.50D) were fitted with reverse geometry OK lenses (BE; Capricornia Contact Lens, Brisbane, Australia) in Boston XO material (nominal Dk/t 46). Lenses were worn overnight only for 14 days. A separate group of 10 subjects (19-32 yrs) wore J-Contour conventional RGP lenses (Capricornia Contact Lens) in Boston XO material (nominal Dk/t 56) for one night in one eye only. Posterior corneal apical radius of curvature (Ro; mm) and asphericity Q were calculated using an in-house program based on the anterior corneal ellipsoid curve measured using the Medmont E300 topographer (Medmont, Camberwell, Australia) and corneal thickness measured with the Holden-Payor optical pachometer across the horizontal meridian. Data were collected at baseline and within 1 hr of eye opening. Repeated measures ANOVA with planned comparisons was used to compare changes from baseline, with a critical p-value of 0.05.

Results: : In the non-lens wearing eye there were no changes in posterior Ro or Q after sleep. In the conventional RGP lens-wearing eyes, there was significant flattening of posterior Ro (p=0.001) and significant increases (towards oblate) in posterior Q (p=0.001) after overnight lens wear. In the OK lens-wearing eyes, myopia reduced from -2.64 ± 0.99D (mean ± SD) to -0.39 ± 0.49D over 14 days of overnight OK. There was significant steepening of posterior Ro in the morning on days 7 and 14 (p<0.001). Moreover, there were significant increases in posterior Q on days 1 (p<0.001) and 4 (p=0.011). In contrast, there was a significant decrease in posterior Q on day 14 (p=0.013).

Conclusions: : The findings of this study are consistent with previous research demonstrating inhibition of central edema in overnight OK, but a normal edema response in the mid-periphery. Analysis relative to a fixed 8mm chord demonstrates that the cornea swells in a posterior direction with overnight edema.

Keywords: contact lens • cornea: clinical science • cornea: basic science 
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